The invention relates to a microcrystalline paraffin, its preparation and its use.
Conventional microcrystalline paraffin obtained from mineral oil (also known as microwaxes) comprises a mixture of saturated hydrocarbons which are solid at room temperature and have a chain length distribution of C25 to C80. In addition to n-alkanes, the microcrystalline paraffins often contain branched isoalkanes and alkyl-substituted cycloalkanes (naphthenes) and proportions—even if generally small ones—of aromatics. The content of isoalkanes and of naphthenes is from 40 to 70%, determined according to EWF Standard Test Method for Analysis of Hydrocarbon Wax by Gas Chromatography. The quantitative dominance of the isoalkanes (and of the naphthenes) is due to their microcrystalline structure.
The solidification range is between 50 and 100° C. according to DIN ISO 2207. The needle penetration has values between 2×10−1 and 160×10−1 mm according to DIN 51579. The solidification point and the needle penetration are used for distinguishing among the microcrystalline paraffins between plastic and hard microcrystalline paraffins. Soft plastic microcrystalline paraffins (so-called petrolatums) are tacky with a very pronounced adhesive power, and they have solidification points of from 65 to 70° C. and penetration values of from 45 to 160×10−1 mm. The oil contents are from 1 to 15%. Plastic microcrystalline paraffins are readily deformable and kneadable and have solidification points between 65 and 80° C. and penetration values of from 10 to 30×10−1 mm. The oil contents may be up to 5%. The hard microcrystalline paraffins are tough and slightly tacky with solidification points of from 80 to 95° C. and penetration values of from 2 to 15×10−1 mm. The oil contents are not more than 2% (cf. Ullmanns Enzyklopädia of Industrial Chemistry, VCH-Verlags-gesellschaft 1996).
Microcrystalline paraffins have a high molar mass and hence high boiling points. They have been obtained to date from the residues of vacuum distillation of mineral oil, in particular in the production of lubricating oil (residue waxes), and from deposits of the mineral oil during its recovery, its transport and its storage, and in technologically very complicated and expensive processes having a plurality of stages, for example deasphalting, solvent extraction, dewaxing, deoiling and refining. The deoiled microcrystalline paraffins contain, as impurity, sulfur, nitrogen and oxygen compounds. They are accordingly not entirely odorless and have a dark yellow to dark brown color. The refinement therefore required is effected, depending on the later application, by bleaching (industrial applications) or by hydrorefining (applications in the food industry and pharmaceutical industry).
Microcrystalline paraffins are used predominantly as components in paraffin or wax mixtures. However, they are generally used in ranges up to 5%. In particular, hardness and melting point of these mixtures are to be increased and flexibility and oil binding capacity improved. Typical applications are, for example, the preparation of waxes for impregnation, coating and lamination for the packaging industry and textile industry, of heatseal and hotmelt adhesives and of pharmaceutical and cosmetic products, including chewing gum. Furthermore, they are used in casting compounds and cable materials and generally in plastics, but also in the candle, rubber and tire industries and in care, antislip and anticorrosion compositions.
DE 69 418 388 T2 describes a hydroisomerization of n-paraffins solid at room temperature and having more than 15 C atoms with use of a catalyst based on a metal of group VIII, in particular platinum, and a borosilicate having a β-zeolite structure to give products which are suitable for the preparation of lubricating oils. (Page 1)
Specifically, the following zeolites were mentioned: omega-zeolite, ZSN-5, X-zeolite, Y-zeolite and further zeolites.
DE 695 15 959 T2 describes the hydroisomerization of wax-containing starting materials to give products which are suitable for the preparation of lubricating oils. A temperature of from 270° to 360° C. and a pressure of from 500 to 1 500 psi or from 3.44 MPa to 10.36 MPa is used for this. The catalyst is based on a catalyzing metal component on a porous, heat-resistant metal oxide support. (cf. page 2, paragraph 1), in particular on from 0.1 to 5% by weight of platinum on alumina or zeolites, such as, for example, offretite, zeolite X, zeolite Y, ZSM-5, ZSM-2, etc. (cf. page 3, middle). The starting materials to be isomerized may be any wax or wax-containing material, in particular also a Fischer-Tropsch wax (cf. page 2, middle). The hydrogen is fed to the reactor at a rate of from 1 000 to 10 000 SCF/bbl and the wax at from 0.1 to 10 LHSV (cf. page 6, middle). The isomerization product is liquid (cf. page 7, line 7). It can be fractionated by distillation or by treatment with solvents, for example with an MEK/toluene mixture (cf. page 7, last paragraph).
The entire liquid product from the isomerization plant is more advantageously treated in a second stage under mild conditions with use of the isomerization catalyst based on a noble metal of group VIII and a heat-resistant metal oxide, in order to reduce PNA and other impurities in the isomerization product and thus to obtain an oil having improved, daylight stability (cf. page 8, paragraph 2). Mild conditions are to be understood as meaning: a temperature in the range from about 170° to 270° C., a pressure of from about 300 to 1500 psi, a hydrogen gas rate of from about 500 to 1 000 SCF/bbl and a flow rate of from about 0.25 to 10 vol./vol./h.
DE 38 72 851 T2 describes the preparation of a middle distillate fuel from a paraffin wax, in particular an FT wax (cf. claim 2), in which the wax is treated with hydrogen under hydroisomerization conditions in the presence of a specific catalyst based on a metal of group VIII, in particular platinum (claim 12), and alumina as support material, so that a medium distillate product and a bottom product having an initial boiling point above 371° C. are obtained (cf. claim 1), in particular a lubricating oil fraction having a low pour point (cf. claim 5). The wax is fed to the reactor at a rate of from 0.2 to 2 V/V. The hydrogen is fed to the reactor at a rate of from 0.089 to 2.67 m3 H2 per 1 l of wax. The catalyst has a decisive influence on the conversion. If it is based on platinum and a β-zeolite having a pore diameter of about 0.7 nm, the desired conversion to a middle distillate product is not observed, in particular with decreasing temperature to 293.9° C. (cf. example 3).